A work vehicle may comprise a combine, a harvester or another work vehicle for harvesting a crop. As crop is harvested, a boundary or edge is formed between the harvested and unharvested crop. The edge may form a generally linear path or a contour that is parallel to previous swaths of the work vehicle in the field, for example. Although a work vehicle may be guided with a location-determining receiver (e.g., a Global Positioning System (GPS) receiver with differential correction), accurate location data to a desired degree of precision may be temporarily unavailable because of propagation problems (e.g., tree canopies) or other technical difficulties. Further, some work vehicles may not be equipped with location-determining receivers that provide location data. For the foregoing reasons, there is a need for a method and system for identifying an edge of crop for guidance of an agricultural machine or other work vehicle.